Pulaski County Coroner's Office personell remove a body after a mother and her four children were found dead in a duplex in Jacksonville, Ark. on Thursday, March 22, 2012.

LITTLE ROCK, Ark. — A mother and four children found dead in a central Arkansas duplex all died accidentally from smoke and soot inhalation, a coroner said Friday.

Gerone Hobbs, coroner for Pulaski County, said it's not clear when the family died. They were found around 7 a.m. Thursday. Fire officials said they suspected the smoke came from an overnight fire that "smoldered itself out" before firefighters arrived.

Phil Nix, executive director of the Jacksonville Housing Authority said a maintenance worker discovered the bodies and that there was extensive smoke damage in the kitchen, particularly near the stove.

Firefighters had responded to reports of smoke at the Jacksonville duplex an hour before the bodies were found, but left when they detected no signs of smoke or heat and no one answered the door.

Authorities said they didn't suspect foul play but continue to investigate whether the fire that killed Marilyn Beavers, 31, her son Dequan Singleton, 11, and daughters Sydni Singleton, 9, Haylee Beavers, 7, and Emily Beavers, 4, was intentionally set.

Jacksonville Fire Marshall Mike Williams said the smoke alarm is being tested as part of the investigation. He said he didn't know if the alarm sounded, but Nix, the housing director, said the device was working.

"When maintenance entered, the first thing they heard was the smoke alarm going off," Nix said.

Each unit has one smoke detector located in the hallway by the bedrooms, he said. Fire extinguishers are not required in the duplex.

Williams said the smoke alarms in the complex are wired in, do not require regular battery replacement, and do not send signals directly to the fire department. He did not know when the last fire inspection of the duplex was conducted.

"We never had a problem with it being out of code," Williams said. "There had never been a complaint."

According to the Arkansas Fire Prevention Code, inspections by local fire departments "shall be made as often as practicable."

Williams said duplexes are "low risk" compared to apartments and have a firewall between the units that take an hour to burn through. The lack of complaints and relative safety of the duplex contribute to the lack of inspections.

"They don't get regular inspections for the most part," he said. "We don't have the manpower."

However, Nix said the housing authority inspects units annually and smoke detectors twice a year. The unit, one of 100 built in the government-run Max Howell Place in 1984, had never had a problem with the smoke detector, he said.